1. Filed of the Invention
The invention relates to a control device for a fluorescent tube supplied from a DC voltage source.
2Description of the Related Art
Lighting of dwellings as well as common or industrial areas uses many fluorescent tubes supplied from an alternating electrical public distribution network of 220V/50 Hz. The specific characteristics of fluorescent tubes require in each lamp the presence of an igniter to start the electrical discharge through the tube and of a ballast to set the intensity of the current in spite of the zone of negative resistance of the voltage/current curve of the tube.
For the control of fluorescent tubes, electronic circuits have been implemented to replace the igniter and the ballast by static semiconductor devices. These circuits are usually resonant converters or accumulating converters.
The proposed devices are in general based on the use of a resonant converter such as the one described in the article: "The electronic control of fluorescent tubes--Michaa el BAIRANZADE--Electronique de puissance No 30". This electroni well adapted to the 220 V/50 Hz local supply area but is not well adapted to function from a low voltage DC source, such as a 12 volt battery. The presence of two power transistors in series in this case leads to energy outputs that are too low, incompatible with a duration between rechargings that would be acceptable by the user. On the other hand, the structure of the accumulating converter is unsuited for use in the local supply area because of the too high voltage imposed on the power transistor. It is perfectly suited, however, for a use at low DC voltage, in a battery. The article: "Un luminaire solaire autonome --Christophe BASSO --Radio Plans No 529" describes the basic principle of such an implementation.